Diagnosis

Gray Coverage Calculator

Type the gray percentage, the natural base, the level and tone you want, and get the natural series share in grams, the developer volume and the processing time.

Free, no sign-up. Runs in your browser. Reviewed 2026-09-04.

The hair in the chair

Estimate per section. Temples usually run higher than the back.

The pigmented hair next to the gray, not the gray itself.

Coverage works best within 1 level of the base.

Hair texture
Gray type

Wiry, glassy white that stayed sheer last time counts as resistant.

Mix this

Natural share1/2 N+ 1/2 6.3
Developer20vol
Processing45min
Coverage confidenceHighopaque pigment

1/2 N + 1/2 target shade: 30 g 6N + 30 g 6.3 (6G), then developer at the brand ratio.

20 vol: enough for 1 level of lift and full coverage.

Apply to the grayest area first, saturate every strand, do not dilute.

If you only read one thing

The natural series share follows the gray percentage: up to 25 percent gray takes 1/4 N, 30 to 50 percent takes 1/2 N, 55 to 75 percent takes 3/4 N, and 80 percent or more takes 100 percent N (NN if it is resistant), all on 20 volume developer. Mix the N at the target level, the one she is going to, and give it 35 to 45 minutes.

Two in the afternoon, seventy percent at the temples

She sits down, pulls her hair back and shows me the temples first. Everyone does. She has put root spray on them that morning and it comes off on my comb as brown dust, so it has to come out at the basin and dry again before I can count, fifteen minutes I had not booked, and she apologizes for it twice, which half my Tuesday clients would not. Seventy percent white at the temples, easy. The back is a different head, twenty percent, scattered, mostly her natural level 5. She wants a warm dark blonde, a 6 with gold in it. And she wants it to stay covered this time, which usually means one bowl went on the whole head.

So, the numbers. Seventy at the temples puts the natural share at three quarters. Twenty through the back puts it at one quarter. A 6 is one level above her base, so 20 volume handles it. Two bowls on one head: 45 g of 6N with 15 g of 6.3 for the hairline and temples, 15 g of 6N with 45 g of 6.3 through the back. I once swapped those bowls, 1/4 N on seventy percent temples, see-through by the second shampoo, and the free redo nine days later cost 60 g of color and an hour, so the temple formula goes in the black bowl now.

For her the calculator runs twice.

Percent gray decides the natural share, nothing else does

Texture moves the timing and the target level moves the developer. The natural share comes from one number: the white in the section I am about to paint, counted by eye on a clean dry parting.

Gray in the sectionNatural series shareIn a 60 g formula
0 to 25 percent1/4 N15 g N + 45 g target shade
30 to 50 percent1/2 N30 g N + 30 g target shade
55 to 75 percent3/4 N45 g N + 15 g target shade
80 to 100 percent100 percent N, or NN if resistant60 g N, gloss for tone after

Estimate by section, because temples and nape are rarely the same number. (Overhead salon light makes every parting look grayer than it is, so I count at the window.) Right on one of the table's steps, I go by feel and by what the hair did last time. And mix the N at the level you are going to, so a 5 going to a 6 gets 6N.

Twenty volume does the covering

20 volume opens the cuticle enough for permanent dye to get in and lifts a level if needed, which is nearly every gray client. 30 volume only when the target sits two full levels above the base, and the trade is sheerer white, because the peroxide spends itself lifting. I have never liked it on a gray head; plenty of colorists use it routinely. Three levels or more is a different service: permanent color cannot lift that far and lay down opaque pigment, so lighten first and cover on 20 volume next visit, or steer her to a target within two levels on the level chart.

Going darker is easy on the chemistry and hard on the eye. Drop three or more levels onto a lot of white and it can go flat, even faintly green, with no warm underlying pigment to hold the depth, so add gold or copper, or pre-fill.

Do not thin the bowl No extra developer to make it spread, and no conditioner or water. Diluted color is the fastest route to a translucent temple. Mix at the brand ratio by weight and weigh both halves.

Why white hair fights you

There is no pigment in the strand, so whatever you deposit is all anyone sees, and a sheer shade that looks rich over a level 6 base is tinted glass over white. The cuticle on gray, especially at the front hairline, often lies tighter, and coarse resistant white can be almost glassy, so dye struggles to get in. And white reflects light, so every under-saturated strand shows. Natural series shades carry all three primaries in balance and do the opaque work. Soft, average or resistant the calculator takes on my word, which comes from finger and thumb and is sometimes wrong on a first visit.

Putting it on the head

  1. Start at the grayest area. Temples and front hairline usually, sometimes the crown: the most resistant hair needs the longest contact.
  2. Take quarter-inch subsections at the regrowth and load the brush. Gray wants product on every strand, all the way round, none of it smeared across the top.
  3. Resistant white on a heavy-gray head: pre-soften. Apply the mixed formula, or plain 20 volume, to the white patches for five to ten minutes, then apply fully. Or use the NN shade and skip the step.
  4. Process the full time. 35 minutes is the floor once there is real gray in the mix, 45 for 50 percent and up or anything wiry, and coarse hair earns another five. The processing time calculator adjusts for heat and hair.
  5. Check before you rinse. Wipe a strand at the temple. Still translucent? Five more minutes, then wipe it again.

Tones that lie on white hair

Reds, coppers and violets are gorgeous on pigmented hair and see-through on white. Past 50 percent gray they need a natural at the same level in the bowl, often half a level darker than the target, so the depth reads before the tone does. Ash lies the other way, dull or drifting green on heavy gray because there is no warmth for the blue-green pigment to cancel, so balance it with N and keep the cool to a whisper.

The line I keep on the mixing bench Cover with natural, tone with fashion. Once the white is covered, a demi gloss on 10 volume can push the whole head any direction she likes.

What to tell the client

What I tell her: your white hair needs more of the base shade than the rest, so the temples read a touch softer than the back. We are on 20 volume, which is there to cover, and it needs the full 45 minutes. Book before the regrowth passes half an inch, because fresh white next to covered white is where it looks patchy. More than two levels lighter is two visits. And to skip the spray next time, or at least tell me it is on there.

Gray coverage questions, answered

How do I know what percentage of gray hair I have?

Take one clean, dry section and count how many strands in ten are white. Two or three in ten is 25 percent, half is 50, most of the section with a few dark strands left is 75 or more. Do the temples, the front hairline and the crown separately, because they are almost always grayer than the back and nape and may need their own bowl. And if there is root spray or powder on there, wash it out first, or you are counting the spray.

What developer should I use to cover gray hair?

20 volume, for almost every case. It opens the cuticle enough for permanent color to deposit and gives one level of lift if the target is a touch lighter than the base. 10 volume tends to give sheer, short-lived coverage on gray, and 30 volume spends its strength lifting and leaves less for depositing, so use it only when you need two levels of lift and accept softer coverage.

Why does my gray hair not take color?

Depends which of three things went wrong: too little natural series in the formula, a diluted or under-saturated application, or resistant white hair with a cuticle so tight the dye cannot get in during the time given. Fix the formula first, then the saturation, then add time. If the hair is wiry and glassy, pre-soften with 20 volume or the formula itself for five to ten minutes, or switch to an NN intense natural shade.

Can I cover gray and go lighter at the same time?

One level, yes, on 20 volume. Two levels, yes on 30 volume, with noticeably softer coverage. More than that, no: permanent color cannot lift three levels and lay down opaque pigment in one application. Lighten first, then cover on 20 volume, or pick a target within two levels of the natural base. The level chart shows what each level looks like next to yours.

Why did my gray hair turn green or ashy after coloring?

Honestly, it is usually the ash shade doing exactly what it was built to do. Ash carries blue and green pigment meant to cancel warmth, and white hair has no warmth to cancel, so on a high percentage of gray the ash shows as itself: dull, flat, sometimes faintly green. Going several levels darker onto white can do the same thing because there is no warm underlying pigment to hold the depth. Balance the ash with natural series and add gold or copper when dropping three or more levels.

How long should you leave hair dye on gray hair?

The full time and then some: 35 minutes as a floor, 45 minutes once the gray is 50 percent or more or the hair is resistant, 50 on coarse hair, and fine hair can come off five minutes early; the processing time calculator adjusts for heat, texture and product type.

Results are estimates built from standard colorimetry practice. Products differ by brand and hair differs by head, so always follow the manufacturer's instructions and strand test before a full application.